Apparatus for pneumatically feeding studs to a welding gun

ABSTRACT

A stud welding gun to which studs are sequentially fed by fluid pressure in an axial direction, the gun including a plunger operable to transfer the stud to a welding position and retain it during welding, and a fluid pressure stream coaxial with the plunger for urging the stud toward the welding position, thereby preventing stud jams within the gun.

United States Patent Ettinger [451 Sept. 26, 1972 [54] APPARATUS FORPNEUMATICALLY [56] References Cited FEEDING STUDS TO A WELDING GUNUNITED STATES PATENTS ml Invent: 322: Emnge" 3,526,744 9/1970 Ehrlich..2l9/98 [73] Assignee: USM Corporation, Warren Division, PrimaryExaminer-R ly Mt. Clemens, Mich. Atrorney--Burton 8!. Parker [22] Filed:Dec. 1, 1971 [57] ABSTRACT [21] Appl' 7 A stud welding gun to whichstuds are sequentially fed r by fluid pressure in an axial direction,the gun includ- 52 us. Cl ..219/9s g a plunger operable to transfer thestud to a ld- 511 Int. Cl. ..B23k 9/00 ing Position and retain it duringg. and fluid 581 Field of Search ..2l9/98, 99 Pressure Stream coaxialwith the plunger for urging the i stud toward the welding position,thereby preventing stud jams within the gun.

5 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION The presentinvention relates to welding guns of the type wherein studs arevsequentially fed to the gun In delivering elongate studs to weldingguns, it has been the practice to provide a stud conduit communicatingat one end with a source'of studs and at the other end with an axiallyaligned inlet passage to the gun. The inlet passage is disposed to anacute angle to a stud delivery passage in the gun, and a reciprocableplunger operates to deliver the stud to' welding position in the guncollet and to back up the stud during the welding operation. Bothgravity and fluid pressure feeds have been employed. I

The above described systems function satisfactorily as long as the gunstud delivery passage is maintained in a downwardly extendingpositioncausing the stud to be urged by gravity through the passage toward thecollet. However, even if a fluid pressure stud feed system is utilized,when the gun is held so that the stud delivery passage extends upwardlyfrom the inlet, the pressure of the fluid is frequently insufiicient topropel the stud completely into the gun delivery passage and maintain itthere until it is picked up by the plunger. Frequently the stud willfall back toward the inlet, and will be only partially in the gundelivery passage when the plungeris shifted, thereby causing a jamwithin the gun. When this occurs, the stud must be cleared beforeanother stud can'be welded. This is time consuming, and is intolerablein a production environment.

The instant invention is directed to the provision of a stud feed assistin the welding gun whichensures that .each stud.delivered to the gun isproperly oriented wholly within the gundelivery passage uponactuation ofthe plunger to transfer the stud through the delivery passage to itswelding position in the gun collet.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERREDEMBODIMENTS Referring now to the drawings, in FIG. 1 there is shown awelding gun 20, which may be of any desired configuration, but isillustrated as a pistol, having a handle 22 and a barrel 24, with theformer provided with a trigger or actuating button 26. The barrel 34 isprovided at its forward end with a collet assembly 28 including a hollowcollet 30 adapted to hold a stud S in position for welding, and at itsrear end'with a fluid pressure cylinder 32, within which is disposed apiston 34 having a projectingplunger 36.

Establishing communication between collet 30 and cylinder 32 is a studdelivery passage 38 extending longitudinally therebetween. Intermediateopposite ends of passage 38 and positioned at an acute angle withrespect thereto, is a stud inlet passage 40, opening through the barrelwall, in spaced-apart, axial alignment with a stud delivery conduit, thedownstream end of which is schematically shown at 42. The end of conduit42 is secured in any convenient fashion to the gun,

the details of the connection not being shown in the interest ofclarity.

It is to be understood that while the instant invention is notspecifically concerned with the exact character of the welding gun,i.e., whether it be of the drawn arc, percussive, or some other type, itwill be obvious to those skilled in the art that the gun 20 may beprovided with suitable structure to enable proper operation in one ofthe many known welding modes. For example, the gun 20 may be constructedin accordance with the disclosure of U. S. Pat. No. 3,546,419, whichshows a so-called drawn arc weldinggun. Neither does the exact type ofstud feeding device employed to feed the studs sequentially through theconduit 42 matter, and various stud feeders may be employed, such asvibratory, oscillating or rotating drum, all of which are known in theart. I

The cylinder-piston motor 32, 34 is a double acting, pneumatic motor,air being supplied to opposite ends of the cylinder through passages 44and 46 which are connected by flexible conduits (not shown) to a sourceof air. under pressure. The portion of the passage 38 between inletpassage 40 and cylinder 32, indicated by numeral 48, embraces plungerrod 36, and is dimensioned slightly oversize so as to permit air to flowaround and past the rod' for the purpose to be described. For example,with a cylindrical rod 36 having a diameter of 0.187 inches, the passage48 has a diameter between 0.195 and 0.200 inches.

Shown in'FIGS. 2 and 3 are-simplified electrical and pneumatic controlcircuits for controlling the sequential operation of the system of whichthe gun is a part, and only that portion of the controlcircuitsnecessary to an understanding of the invention has been shown.Briefly, the electrical circuit includes a control relay CR-l coupled toa source of DC. power, the relay having a set of normally open contactsCRl-l. A 115 volt AC control circuit as shown includes the contacts CR1-1, a pair of time delay relays TD-l and TD-2 and a pair of solenoidoperated valves SOL.1 and SOL.2.

Assuming that a stud S has been delivered to gun 20, and that airpassage 46 has been pressurized to shift plunger rod 36 forwardly toshift the stud to its welding position shown in FIG. 1 and support itduring welding, actuation of trigger 26 on the gun initiates the weldingcycle, at the conclusion of which relay CR-l is energized, closingcontacts CRl-l in the control circuit. This energizes TD-l, immediatelyclosing its normally open contacts TDl-l, thereby energizing TD-2 also.Contacts TDl-3 are also closed, completing the circuit to solenoid SOLJ,which controls a four-way valve V-l (FIG. 3). Energization of SOL.1shifts valve V-l to its position pressurizing lines 50 and 44, theformer acclosing contacts TD2-l to energize solenoid SOL.2, which shiftsvalve V-2 to pressurize conduit 42, thereby blowing the studtherethrough and into stud entry passage 40 in gun 20. As the end ofconduit 42 is spaced from the entrance port of passage 40, much of thestud delivery air under pressure will be dissipated, and the stud maynot be delivered far enough by the air in conduit 42 to assume itsposition wholly within passage 38, particularly if the gun is held withthe collet 30 pointing upwardly. It the stud lies partially in passage38 and partially in passage 40 when the plunger rod 36 shifts forwardly,a jam will result and the stud will not be transferred to its weldingposition.

In order to obviate any stud jams within the gun 20, the passage portion48 is slightly oversize the plunger rod 36, as pointed out above,whereby upon the pressurization of air passage 44 to retract the plunger36 pressure air is also supplied to passage 38 through portion 48 toensure stud delivery completely into passage 38. I

When piston 34 is retracted by the actuation of Valve V-l pressurizingline 44, lane 50 is also pressurized to deliver a stud to deliveryconduit 42. Air in gun cylinder 32,in addition to retracting the piston34, flows through passage portion 48 and delivers a stream of pressureair axially through passage 38 toward and out of collet 30. Subsequentactuation of valve V-2 delivers the stud under air pressure throughconduit 42, and as the stud enters through inlet passage 40, it ispicked up by the air stream flowing axial of passage 38 and urged towardcollet 30. Thereafter four way valve V-l is reversed, pressurizing line46 to shift plunger 36 forward, thereby seating the stud in the colletin its welding position as shown in FIG. 1.

What is claimed is:

1. In a stud welding system, a stud welding tool having a stud retainingcollet at one end of the tool, a longitudinally extending stud deliverypassage in the tool extending rearwardly of said collet and having alaterally opening stud inlet spaced from the collet, a stud feed conduithaving a downstream end coupled to the tool with its outlet disposed inspaced aligned confrontation with said passage inlet, a fluid pressurecylinder in said tool spaced rearwardly of said passage, a piston insaid cylinder with a plunger rod coupled thereto projecting into saidpassage for transferring a stud received through said inlet into saidstud retaining collet, fluid conducting passageway means establishingcommunication between said cylinder and the rear end of said studdelivery passage, and means for introducing fluid under pressure intosaid cylinder to retract said piston and rod and to direct pressurefluid through said passage-way means into the stud delivery passage forurging a stud therein toward said collet.

2. The invention as defined in claim 1 characterized in that said fluidconducting passageway means is disposed in axial alignment between saidstud delivery passage and said cylinder and is sized to accommodate saidplunger rod, with the rod projecting through the passageway and thepressure fluid delivered therethrough around the rod.

3. The invention as defined in claim 2 characterized in that said fluidpressure cylinder is double acting, having fluid pressure inlets atopposite ends thereof to shift the piston and plunger rod in bothdirections. I

4. The invention as defined 1n cla1m 3 characterized in that said systemincludes stud delivery means connected to said feed conduit fordelivering studs therethrough one at a time, electric supply meansconnected to said tool for supplying welding current thereto, andcontrol means coupled to said delivery means, said electric supply meansand said fluid introducing means for controlling the sequentialoperation of all of said means.

5. The invention as defined in claim 4 characterized in that saidcontrol means includes means for actuating the fluid introducing meansand the stud delivery means in response to the culmination of a weldingoperation to deliver a stud and retract the plunger rod and maintainpressure fluid supply through said fluid conducting passageway for apredetermined time sufficient to insure stud delivery through said studinlet and toward said collect.

1. In a stud welding system, a stud welding tool having a stud retainingcollet at one end of the tool, a longitudinally extending stud deliverypassage in the tool extending rearwardly of said collet and having alaterally opening stud inlet spaced from the collet, a stud feed conduithaving a downstream end coupled to the tool with its outlet disposed inspaced aligned confrontation with said passage inlet, a fluid pressurecylinder in said tool spaced rearwardly of said passage, a piston insaid cylinder with a plunger rod coupled thereto projecting into saidpassage for transferring a stud received through said inlet into saidstud retaining collet, fluid conducting passageway means establishingcommunication between said cylinder and the rear end of said studdelivery passage, and means for introducing fluid under pressure intosaid cylinder to retract said piston and rod and to direct pressurefluid through said passage-way means into the stud delivery passage forurging a stud therein toward said collet.
 2. The invention as defined inclaim 1 characterized in that said fluid conducting passageway means isdisposed in axial alignment between said stud delivery passage and saidcylinder and is sized to accommodate said plunger rod, with the rodprojecting through the passageway and the pressure fluid deliveredtherethrough around the rod.
 3. The invention as defined in claim 2characterized in that said fluid pressure cylinder is double acting,having fluid pressure inlets at opposite ends thereof to shift thepiston and plunger rod in both directions.
 4. The invention as definedin claim 3 characterized in that said system includes stud deliverymeans connected to said feed conduit for delivering studs therethroughone at a time, electric supply means connected to said tool forsupplying welding current thereto, and control means coupled to saiddelivery means, said electric supply means and said fluid introducingmeans for controlling the sequential operation of all of said means. 5.The invention as defined in claim 4 characterized in that said controlmeans includes means for actuating the fluid introducing means and thestud delivery means in response to the culmination of a weldingoperation to deliver a stud and retract the plunger rod and maintainpressure fluid supply through said fluid conducting passageway for apredetermined time sufficient to insure stud delivery through said studinlet and toward said collect.